[Feature-Request] set default zoom level for collections in config

[LeonNamowitz]

Is your feature request related to a problem? Please describe.
Some of my collections with only a dozen or so images in them look weirdly "zoomed out" with the default image_height=100 parameter (the middle one in the UI). So I always end up switching the zoom in the UI to the biggest one (image_height=300), but I have to repeat it every time I open another collection.

You can kind of see it in the demo even. Where the default looks empty, and arguably even the biggest UI selectable value is too small. While e.g. image_height=600 looks way better (okay maybe not in this album but you get the idea I hope).

Describe the solution you'd like
I would love to be able to set the default image_height value for a collection (or rather all of them, all expanded ones as well) in the config.yaml.
Arbitrary values ideally, like you already can by editing that part of the URL.
I think it just works with the Album, Timeline and Flex layouts.

# Screencaps folder
  - name: Screencaps
    layout: flex
    sort: -date
    image_height: 500
    dirs:
      - /Screencaps

Describe alternatives you've considered
I tried different layouts but since it kind of looks different depending on how many images are in a collection there is no perfect default currently.

Additional context
Honestly it would also be great to be able to change the 3 different values presented in the UI, image_height=30, image_height=100 and image_height=300 to other values since sometimes even 300 is a little small imo. But that is not as important if I can set the default in the config.

[SmilyOrg]

Hey, this is a good one! #104 might also help here :)

[LeonNamowitz]

Like you wrote there flex already kind of does this, except the biggest size is too small for few images.
Ideally my default would be flex at like image_height=600 or so